Metal-dependent, NAD+-dependent formate dehydrogenases are complex metalloenzymes coupling biochemical transformations through intricate electron transfer pathways. The formate dehydrogenase from Rhodobacter capsulatus is a model enzyme for understanding coupled catalysis, in that reversible CO2 reduction and formate oxidation are linked to a flavin mononuclotide (FMN)-bound diaphorase module via seven iron-sulfur (Fe-S) clusters per protomer. Catalysis occurs at a bis-metal-binding pterin (Mo) binding two molybdopterin guanine dinucleotides (bis-MGD), a protein-based Cys residue and a participatory sulfido ligand. Overall, formate dehydrogenases catalyze the reversible oxidation of formate to carbon dioxide. These enzymes play an important role in CO2 reduction and serve as nicotinamide cofactor recycling enzymes. More recently, the CO2-reducing activity of formate dehydrogenases, especially a metal-containing formate dehydrogenase, has been further explored for efficient atmospheric CO2 capture. Along this line, molecular hydrogen (H2) as the fuel of the future represents an efficient, cheap and environmentally friendly reducing agent when produced from renewable sources. Herein, we investigate the coupling between FDH and hydrogenase or photosystem I for hydrogen- and light-driven CO2 reduction using the molybdenum-dependent formate dehydrogenase from Rhodobacter capsulatus.